Water Recharge & Availability
VulnerabilityAquifer vulnerability is rooted in geology.
Precipitation in the Portneuf Valley is rather low (10-12”/year). This does not allow for much recharge into the aquifer. Most of the water runs off of lawns and City streets into the storm drain system and into the Portneuf River. Most of the recharge for our aquifer occurs in the Upper Mink Creek/Gibson Jack/Scout Mountain area where there is 30”/year of precipitation. Most of it falls as snow and melts into the ground. It flows through the ground into the Lower Portneuf Valley Aquifer.
In this picture you can see the snowpack in the Upper Gibson Jack/Scout Mountain Areas. When this snow melts it infiltrates into the ground, recharging our aquifer.
Aquifer Water Volume and Use
Where does our water come from?
- 80% of our water (5.4 billion gallons/year) come from the Scout Mtn – Gibson Jack area.
- 15% (1.1 billion gallons/year) come through the Portneuf Gap (underground)
- 5% (less than 0.5 billion gallons/year) come out of Pocatello Creek area (underground)
- In red is the amount the cities of Pocatello and Chubbuck pump out of the aquifer:
- We pump 1.1 billions gallons/year out of the southern aquifer (as a result only 5.3 billion gallons/year flow from the southern aquifer into the northern aquifer)
- We pump 6.1 billion gallons/year out of the northern aquifer
- In dry years we may take water in from the Snake River Aquifer. In wet years we discharge a small volume of water into the Snake River Aquifer
- In general we pump out 7.8 billion gallons/year. Our water recharge (primarily from snowmelt) is a similar amount. However, in some recent years we have taken out more than was put in through recharge.